1. Field of the Invention
This invention relates generally to T-handle lock assemblies and more particularly to improvements in security and serviceability features of the handle and handle extension of high security T-handle lock assemblies.
2. Background and Prior Art
T-handle lock assemblies are commonly used to restrict access to vending machines and the like such as soft drink or food vending machines, currency changers, transit system fare collection machines, storage modules, and outdoor utility boxes. Because of the valuable nature of the contents of such machines and the usually unattended locations at which such machines and boxes are situated, such lock assemblies are highly susceptible to attack by thieves and others and require frequent servicing or replacement.
T-handle lock assemblies are known in the art. See, e.g., U.S. Pat. Nos. 3,089,329, 3,089,330, 4,132,092, 4,552,001, and 4,835,998.
Some years ago T-handles and extensions for T-handle locks were typically made of a single piece die cast material such as zinc which was relatively easy to break by hammering or prying and which did not provide much protection for the lock cylinder located within the extension. An improvement to the one piece T-handle is disclosed in aforementioned U.S. Pat. No. 4,552,001. The improved T-handle assembly includes a separate stainless steel cylinder front handle and cylinder/extension housing which connect to each other by virtue of bayonet type tabs on the end of the housing mating with corresponding slots in the front handle. The front handle contains a pair of small diameter holes which extend past the slots for insertion of metal driving pins to hold the tabs in place. The front handle provides greater security by preventing pulling of the lock cylinder from the front. However, the manufacturing process for this device is difficult and expensive since transverse-hole drilling of the stainless steel front handle is required. Additionally, removal of the driving pins is difficult and time consuming which increases the cost of servicing the lock assembly.
Another prior art approaach to improving the one piece die cast T-handle and extension is shown in U.S. Pat. No. 4,835,998. This patent shows a hollow steel front handle and a diecast extension piece having an inner handle. The front handle is attached to the inner handle by four set screws which are inserted into corresponding holes which must be drilled and tapped into the front handle. This combination suffers from a high cost of manufacturing due to the requirement for drilling and tapping four holes for the front handle set screws. In addition, servicing of the assembly is complicated by the need to remove and replace four set screws. The diecast inner handle/extension component is relatively weak and is subject to fracturing under attack, while the front handle may be removed by breaking away the outer housing and removing the set screws, thus providing access to the lock cylinder.
Thus, there remains a need in the art for an improved T-handle assembly which is easily manufactured and serviced and which provides a high degree of security against physical attack.